Didn't you watch the devstream? 🤔
Kuva Lich system will be bleeding all over your map so you know that you should care about it.
Then Kuva Lich will steal your loot (and you can only get MOST of it back but NOT all of it when you defeat them - potentially so you'll have an incentive to care about the bleeding nodes and HOPEFULLY get your Ephemera blueprint back).
Then Kuva Lich will haunt you in missions like syndicates / stalker / etc, except they have fancy finisher animations if they can kill you.
And in order to properly kill the Kuva Lich, you need to use the new system "Parazon Immortal Mods" where you must combine 3+ immortal mods (that you had to farm from somewhere) in a given arbitrary/random order that RNG gave you when it spawned your Kuva Lich, and you have to do guess-work to figure out whether you successfully put together the correct random order of immortal mods or not, potentially never seeing your loot again unless you manage to set up the right mod order over the span of 10+ missions where you actually managed to encounter the Kuva Lich (for which you had to farm the bleeding map nodes to increase the spawn rates)
You can't use your "powerful builds" for it, you have to mess around with the Parazon mods and hope for the best (whether you successfully kill it or not, and whether you get your rare loot back or not). 🙄
So it's not about build optimization, it's about micro-managing your Parazon until the next Stalker Kuva Lich attack, where the condition for success is 100% randomized, and potentially also depends on whether you were lucky to find the immortal mod you actually need to kill it.
In short, you're forced to gamble for your loot, AFTER successfully getting it out of the RNG machine's 1% chance of an ephemera / braton vandal blueprint or a 0.1% of a condition overload. You think you got it? Nope gotta kill the Kuva Lich first (why else would you want to farm the immortal mods? 3k MR? Although tbh I'd do it for the MR, I don't like the idea of this kind of "forced" incentive at all to slow down your progress)